Re: [PATCH v2] mm/compaction: __compact_pgdat() code cleanuup

From: David Rientjes
Date: Wed Nov 25 2015 - 05:45:23 EST


On Wed, 25 Nov 2015, Joonsoo Kim wrote:

> This patch uses is_via_compact_memory() to distinguish direct compaction.

When I think of "direct compaction", I think of compaction triggered for
high-order allocations from the page allocator before direct reclaim.
This is the opposite of being triggered for is_via_compact_memory().

> And it also reduces indentation on compaction_defer_reset
> by filtering failure case. There is no functional change.
>
> Acked-by: Yaowei Bai <baiyaowei@xxxxxxxxxxxxxxxxxxxx>
> Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>
> ---
> mm/compaction.c | 13 +++++++------
> 1 file changed, 7 insertions(+), 6 deletions(-)
>
> diff --git a/mm/compaction.c b/mm/compaction.c
> index de3e1e7..01b1e5e 100644
> --- a/mm/compaction.c
> +++ b/mm/compaction.c
> @@ -1658,14 +1658,15 @@ static void __compact_pgdat(pg_data_t *pgdat, struct compact_control *cc)
> !compaction_deferred(zone, cc->order))
> compact_zone(zone, cc);
>
> - if (cc->order > 0) {
> - if (zone_watermark_ok(zone, cc->order,
> - low_wmark_pages(zone), 0, 0))
> - compaction_defer_reset(zone, cc->order, false);
> - }
> -
> VM_BUG_ON(!list_empty(&cc->freepages));
> VM_BUG_ON(!list_empty(&cc->migratepages));
> +
> + if (is_via_compact_memory(cc->order))
> + continue;

This will be the third call to is_via_compact_memory() in this function.
Maybe just do

const bool sysctl = is_via_compact_memory(cc->order);

early in the function since it won't change during the iteration? (And
maybe get rid of that extra newline that already exists at the beginning
of the iteration?

Otherwise:

Acked-by: David Rientjes <rientjes@xxxxxxxxxx>
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